Research on the mechanism of alkali leaching disease in cement concrete bridge deck pavements

A novel type of deterioration, known as alkali leaching, increasingly occurs on cement concrete bridge deck pavements, causing unsightly white spots and compromising structural durability. This study clarifies the underlying mechanism, revealing that differential air pressure induced by environmental atmospheric fluctuations drives water migration from internal voids to the surface. Porosity and water level depth emerged as primary factors influencing alkali leaching. CT scanning indicated a non-uniform porosity distribution with higher values at specimen ends and mid-height, and connected pores accounted for 90.2% of total void volume, significantly facilitating leaching. A novel indicator—leaching water mass—was introduced to quantitatively assess leaching severity, with simulated results aligning closely (within 9.8%) with experimental observations. Micro-scale seepage simulations highlighted the critical influence of connected pore morphology on internal water flow. The findings provide insights into water transport mechanisms, aiding future strategies for alkali leaching prevention in concrete bridge decks.